docs: def train_all(ctx, output):
      """Train POS tagger on WSJ, GENIA, and both. With and without cluster features."""
      click.echo('chemdataextractor.pos.train_all')
      click.echo('Output: %s' % output)
      ctx.invoke(train, output='%s_wsj_nocluster.pickle' % output, corpus='wsj', clusters=False)
      ctx.invoke(train, output='%s_wsj.pickle' % output, corpus='wsj', clusters=True)
      ctx.invoke(train, output='%s_genia_nocluster.pickle' % output, corpus='genia', clusters=False)
      ctx.invoke(train, output='%s_genia.pickle' % output, corpus='genia', clusters=True)
      ctx.invoke(train, output='%s_wsj_genia_nocluster.pickle' % output, corpus='wsj+genia', clusters=False)
      ctx.invoke(train, output='%s_wsj_genia.pickle' % output, corpus='wsj+genia', clusters=True)